1. Field of the Invention
The present invention relates to a power unit for a motorcycle that includes an internal combustion engine having a crankcase in which an upper case half body and a lower case half body are joined together at a split face and which rotatably supports a crankshaft with an axial line disposed on the split face and a continuously variable transmission in which a belt is wound around a drive pulley and a driven pulley to which power is transmitted from the crankshaft.
2. Description of Background Art
A power unit for a motorcycle is disclosed in Japanese Patent Laid-Open No. Hei 1-233189 wherein the axial line of a crankshaft and the axial line of the countershaft of a transmission are disposed on the split surface of a crankcase and the main shaft of the transmission is journaled by one of upper and lower case half bodies joined together to form the crankcase.
The power unit for the motorcycle as disclosed in Japanese Patent Laid-Open No. Hei 1-233189 uses the same oil for the lubricating portions of an internal combustion engine and for the transmission. Thus, the associated parts can relatively freely select an arrangement position relative to the main shaft of the transmission with a simplified configuration for the crankcase. Therefore, it is possible to set the split face of the crankcase without considering the mounting performance.
Continuously variable transmissions or the like of types using metal belts are desired to use oil of a different in type from that used for the lubricating portions of the internal combustion engine. In such a case, it is difficult for the configuration of the power unit disclosed in Japanese Patent Laid-Open No. Hei 1-233189 to use two types of respective oils isolated from each other for the internal combustion engine and for the continuously variable transmission. In addition, the power unit for a motorcycle is desired to be superior in case-rigidity as well as to be compact.